PINE-TREE enables highly efficient genetic modification of human cell lines

Prime editing technologies enable precise genome editing without the caveats of CRISPR nuclease-based methods. Nonetheless, current approaches to identify and isolate prime-edited cell populations are inefficient. Here, we established a fluorescence-based system, prime-induced nucleotide engineering using a transient reporter for editing enrichment (PINE-TREE), for real-time enrichment of prime-edited cell populations. We demonstrated the broad utility of PINE-TREE for highly efficient introduction of substitutions, insertions, and deletions at various genomic loci. Finally, we employ PINE-TREE to rapidly and efficiently generate clonal isogenic human pluripotent stem cell lines, a cell type recalcitrant to genome editing.

A microcarrier-based protocol for scalable generation and purification of human induced pluripotent stem cell-derived neurons and astrocytes

Here, we describe a protocol for a microcarrier (MC)-based, large-scale generation and cryopreservation of human-induced pluripotent stem cell (hiPSC)-derived neurons and astrocytes. We also detail steps to isolate these populations with a high degree of purity. Finally, we describe how to cryopreserve these cell types while maintaining high levels of viability and preserving cellular function post-thaw. For complete details on the use and execution of this protocol, please refer to Brookhouser et al. (2021).

APOE2 mitigates disease-related phenotypes in an isogenic hiPSC-based model of Alzheimer's disease

Genome-wide association studies (GWAS) have identified polymorphism in the Apolipoprotein E gene (APOE) to be the most prominent risk factor for Alzheimer's disease (AD). Compared to individuals homozygous for the APOE3 variant, individuals with the APOE4 variant have a significantly elevated risk of AD. On the other hand, longitudinal studies have shown that the presence of the APOE2 variant reduces the lifetime risk of developing AD by 40 percent. While there has been significant research that has identified the risk-inducing effects of APOE4, the underlying mechanisms by which APOE2 influences AD onset and progression have not been extensively explored. In this study, we utilize an isogenic human induced pluripotent stem cell (hiPSC)-based system to demonstrate that conversion of APOE3 to APOE2 greatly reduced the production of amyloid-beta (Aβ) peptides in hiPSC-derived neural cultures. Mechanistically, analysis of pure populations of neurons and astrocytes derived from these neural cultures revealed that mitigating effects of APOE2 are mediated by cell autonomous and non-autonomous effects. In particular, we demonstrated the reduction in Aβ is potentially driven by a mechanism related to non-amyloidogenic processing of amyloid precursor protein (APP), suggesting a gain of the protective function of the APOE2 variant. Together, this study provides insights into the risk-modifying effects associated with the APOE2 allele and establishes a platform to probe the mechanisms by which APOE2 enhances neuroprotection against AD.

The sclerostin-neutralizing antibody AbD09097 recognizes an epitope adjacent to sclerostin's binding site for the Wnt co-receptor LRP6

The glycoprotein sclerostin has been identified as a negative regulator of bone growth. It exerts its function by interacting with the Wnt co-receptor LRP5/6, blocks the binding of Wnt factors and thereby inhibits Wnt signalling. Neutralizing anti-sclerostin antibodies are able to restore Wnt activity and enhance bone growth thereby presenting a new osteoanabolic therapy approach for diseases such as osteoporosis. We have generated various Fab antibodies against human and murine sclerostin using a phage display set-up. Biochemical analyses have identified one Fab developed against murine sclerostin, AbD09097 that efficiently neutralizes sclerostin's Wnt inhibitory activity. In vitro interaction analysis using sclerostin variants revealed that this neutralizing Fab binds to sclerostin's flexible second loop, which has been shown to harbour the LRP5/6 binding motif. Affinity maturation was then applied to AbD09097, providing a set of improved neutralizing Fab antibodies which particularly bind human sclerostin with enhanced affinity. Determining the crystal structure of AbD09097 provides first insights into how this antibody might recognize and neutralize sclerostin. Together with the structure-function relationship derived from affinity maturation these new data will foster the rational design of new and highly efficient anti-sclerostin antibodies for the therapy of bone loss diseases such as osteoporosis.

Neuropsychological course of voltage-gated potassium channel and glutamic acid decarboxylase antibody related limbic encephalitis

BACKGROUND AND PURPOSE

Autoantibodies (abs) to glutamic acid decarboxylase (GAD) and to voltage-gated potassium channels (VGKC) induce distinct courses of limbic encephalitis, related to MRI findings, seizure outcome and cognition.

METHODS

A detailed analysis of the cognitive course of the two forms is presented, spanning a median time interval of 28 months, including parameters of attention, learning and memory in 15 VGKC-ab-positive and 16 GAD-ab-positive patients.

RESULTS

In both groups, the initially significantly impaired attention performance recovered to a putatively premorbid level. In VGKC patients the partially severely impaired learning and memory performance improved under treatment but remained subnormal at last follow-up. By contrast, GAD-ab-positive patients had initially less impaired learning and memory scores but did not show an improvement under treatment.

CONCLUSIONS

The results provide evidence of distinct relations between inductive processes and cognitive outcome in VGKC-ab-positive and GAD-ab-positive subforms of limbic encephalitis, which possibly depend on differences in pathogenic molecular mechanisms and affected cerebral loci.

Selecting highly structure-specific antibodies using structured synthetic mimics of the cystine knot protein sclerostin

Antibodies directed against specific regions of a protein have traditionally been raised against full proteins, protein domains or simple unstructured peptides, containing contiguous stretches of primary sequence. We have used a new approach of selecting antibodies against restrained peptides mimicking defined epitopes of the bone modulator protein sclerostin, which has been identified as a negative regulator of the Wnt pathway. For a fast exploration of activity defining epitopes, we produced a set of synthetic peptide constructs mimicking native sclerostin, in which intervening loops from the cystine-knot protein sclerostin were truncated and whose sequences were optimized for fast and productive refolding. We found that the second loop within the cystine knot could be replaced by unnatural sequences, both speeding up folding, and increasing yield. Subsequently, we used these constructs to pan the HuCAL phage display library for antibodies capable of binding the native protein, thereby restricting recognition to the desired epitope regions. It is shown that the antibodies that were obtained recognize a complex epitope in the protein that cannot be mimicked with linear peptides. Antibodies selected against peptides show similar recognition specificity and potency as compared with antibodies obtained from full-length recombinant protein.

Stimulus complexity dependent memory impairment and changes in motor performance after deletion of the neuronal gap junction protein connexin36 in mice

Gap junction channels, composed of connexin (Cx) proteins, are conduits for intercellular communication and metabolic exchange in the central nervous system. Connexin36 (Cx36) is expressed in distinct subpopulations of neurons throughout the mammalian brain. Deletion of the Cx36 gene in the mouse affected power and frequency of gamma and sharp wave-ripple oscillations, putative correlates of memory engram inscription. Here, we present a behavioral analysis of Cx36-deficient mice. Activity patterns, exploratory- and anxiety-related responses were largely unaffected by elimination of Cx36, while sensorimotor capacities and learning and memory processes were impaired. Repeated testing on the rotarod suggested that the Cx36-deficient mice showed slower motor-coordination learning. After a retention interval of 24 h the Cx36-deficient mice showed habituation to an open-field, but failed to habituate to a more complex spatial environment (Y-maze). A more pronounced memory impairment was found when Cx36 knockout mice had to remember recently explored objects. Cx36-deficient mice were unable to recognize objects after short delays of 15 and 45 min. These data suggest that lack of Cx36 induces memory impairments that vary in dependence of the complexity of the stimuli presented. Our results suggest that neuronal gap junctions incorporating Cx36 play a role in learning and memory.

Dose escalation study for defining the maximum tolerated dose of continuous oral trofosfamide in pretreated patients with metastatic lung cancer

BACKGROUND

Trofosfamide is increasingly used in the treatment of patients with several types of malignancies. However, the optimal dose of trofosfamide for patients with advanced cancer has not been systematically investigated yet. The aim of this study was to define the maximum tolerated dose (MTD) of continuous oral trofosfamide.

PATIENTS AND METHODS

16 patients with advanced lung cancer (14 nonsmall cell lung cancer, 2 small cell lung cancer; 10 male, 6 female; median age 64 years (range 46-82); median Karnofsky status 70%; median number of organs involved 3 (range 1-6)) were enrolled. All patients were previously treated with chemotherapy (median 2x, range 1-6) and 8/16 (50%) with radiotherapy. Patients received trofosfamide p.o. administered in 3 doses per day for 3 weeks (1 cycle) using a 3-patient-cohort dose-escalation strategy. Toxicities were graded according to the WHO Criteria.

RESULTS

Patients received a median of 2 cycles of trofosfamide (range 1-4) at 3 dose levels (90, 125, and 175 mg/m2). Grade 3 and 4 neutropenia, anemia, and thrombocytopenia were observed in 20, 13.3, and 6.6%, respectively. Dose-limiting toxicities during the first cycle were grade 3 muscle weakness and anorexia observed in 1/6 patients in cohort 1 (trofosfamide 90 mg/m2), grade 3 neutropenia in 1/6, and encephalopathy in 1/6 patients in cohort 3 (trofosfamide 175 mg/m2). Therefore, the dose level of 125 mg/m2 was defined as the MTD.

CONCLUSION

Trofosfamide at 125 mg/m2 administered in 3 doses per day was well tolerated. This dose level is recommended for further clinical studies.

Connexin30-deficient mice show increased emotionality and decreased rearing activity in the open-field along with neurochemical changes

Gap-junction channels in the brain, formed by connexin (Cx) proteins with a distinct regional/cell-type distribution, allow intercellular electrical and metabolic communication. In astrocytes, mainly the connexins 43, 26 and 30 are expressed. In addition, connexin30 is expressed in ependymal and leptomeningeal cells, as well as in skin and cochlea. The functional implications of the astrocytic gap-junctional network are not well understood and evidence regarding their behavioural relevance is lacking. Thus, we have tested groups of Cx30-/-, Cx30+/-, and Cx30+/+ mice in the open-field, an object exploration task, in the graded anxiety test and on the rotarod. The Cx30-/- mice showed reduced exploratory activity in terms of rearings but not locomotion in the open-field and object exploration task. Furthermore, Cx30-/- mice exhibited anxiogenic behaviour as shown by higher open-field centre avoidance and corner preference. Graded anxiety test and rotarod performance was similar across groups. The Cx30-/- mice had elevated choline levels in the ventral striatum, possibly related to their aberrant behavioural phenotypes. The Cx30+/- mice had lower dopamine and metabolite levels in the amygdala and ventral striatum and lower hippocampal 5-hydroxyindole acid (5-HIAA) concentrations relative to Cx30+/+ mice. Furthermore, the Cx30+/- mice had lower acetylcholine concentrations in the ventral striatum and higher choline levels in the neostriatum, relative to Cx30+/+ mice. Our data suggest that the elimination of connexin30 can alter the reactivity to novel environments, pointing to the importance of gap-junctional signalling in behavioural processes.

High-frequency oscillation in the hippocampus of the behaving rat and its modulation by the histaminergic system

The histaminergic neurons located in the posterior hypothalamus modulate whole brain activity in a manner dependent on behavioral state. We have investigated their influence on high-frequency oscillation (200-Hz ripples) in the hippocampal CA1 region of freely moving rats. The occurrence of these ripples, assumed to be involved in memory trace formation, was markedly enhanced after injection of the H1-antagonists pyrilamine and ketotifen in a lateral ventricle, indicating a tonic activity of the histaminergic system. The H2- and H3-antagonists cimetidine and thioperamide were ineffective. We suggest a mediation of these effects through blocking the known histaminergic excitation of septal neurons. Histamine administered by the intracerebroventricular route had an inhibitory action on ripples. H1-receptor activation, which has been shown to inhibit learning and memory, thus shifts hippocampal activity away from high-frequency oscillation toward theta activity.

Aged endothelial nitric oxide synthase knockout mice exhibit higher mortality concomitant with impaired open-field habituation and alterations in forebrain neurotransmitter levels

Endothelial nitric oxide synthase (eNOS) has been implicated in various brain and peripheral pathologies such as renal failure, heart failure or stroke. Consequently, the mortality rate of aged eNOS knockout mice (eNOS-/-) was higher than that of age-matched (18-22 months old) controls. Only seven of the original 14 eNOS-/- animals that participated in the study reached the age of 18 months or older, whereas no control mice died during this life span. In order to assess the behavioral and neurochemical consequences of chronic eNOS deficiency we examined whether the surviving aged eNOS-/- mice showed changes in terms of motor, emotional, exploratory and neurochemical parameters. Aged eNOS-/- mice showed reduced exploratory activity in the open-field with no habituation observable neither within sessions nor after repeated exposures. Pole test performance of eNOS-/- mice was comparable to controls. In the elevated plus-maze eNOS-/- mice did not differ from controls in terms of time spent in and entries into arms, but showed less locomotion on the open arms. The most prominent neurochemical alterations in the forebrains of aged eNOS-/- mice were: (a) increased acetylcholine levels in the neostriatum; (b) decreased noradrenaline concentrations in the ventral striatum; and (c) lower serotonin levels in the frontal cortex and ventral striatum. The present findings suggest that mice which survived chronic eNOS-deficiency into old age, show some behavioral and neurochemical phenotypes distinct from adult eNOS-/- mice.

Unaltered radial maze performance and brain acetylcholine of the endothelial nitric oxide synthase knockout mouse

Proceeding from previous findings of a beneficial effect of endothelial nitric oxide synthase (eNOS) gene inactivation on negatively reinforced water maze performance, we asked whether this improvement in place learning capacities also holds for a positively reinforced radial maze task. Unlike its beneficial effects on the water maze task, eNOS gene inactivation did not facilitate radial maze performance. The acquisition performance over the days of place learning did not differ between eNOS knockout (eNOS-/-) and wild-type mice (eNOS+/+). eNOS-/- mice displayed a slight and eNOS+/+ mice a more severe working memory deficit in the place learning version of the radial maze compared to the genetic background C57BL/6 strain. Possible differential effects of eNOS inactivation, related to differences in reinforcement contingencies between the Morris water maze and radial maze tasks, behavioral strategy requirements, or to different emotional and physiological concomitants inherent in the two tasks are discussed. These task-unique characteristics might be differentially affected by the reported anxiogenic and hypertensional effects of eNOS gene inactivation. Post-mortem determination of acetylcholine concentrations in diverse brain structures revealed that acetylcholine and choline contents were not different between eNOS-/- and eNOS+/+ mice, but were increased in eNOS+/+ mice compared to C57BL/6 mice in the frontal cortex. Our findings demonstrate that phenotyping of learning and memory capacities should not rely on one learning task only, but should include tasks employing both negative and positive reinforcement contingencies in order to allow valid statements regarding differences in learning capacities between rodent strains.

Comparison of intra-accumbens injection of histamine with histamine H1-receptor antagonist chlorpheniramine in effects on reinforcement and memory parameters

Histaminergic neurons are located exclusively in the tuberomammillary nuclei (TM) of the hypothalamus from where they project to many regions of the brain including the basal ganglia. Earlier experiments led to the hypothesis that neuronal histamine (HA), particularly in relation to the H1 receptor, has an inhibitory role in learning and reward-related processes. Based on this premise, the objective of the present study was to compare HA with the H1-receptor antagonist d-chlorpheniramine (CPR) in effects on reinforcement and memory parameters after injection into different subregions of the rat nucleus accumbens (NAcc). In the first experiment, mnemoactive effects of CPR (0.1-10 microg) were assessed after injection into the caudal or rostral part of the NAcc with the one-trial uphill avoidance task as a measure of learning. The data show that intra-NAcc injection of CPR (10 microg) facilitated retention of the task, when the compound was administered immediately after training. This effect was evident only when CPR was administered into the caudal-shell but not into the rostral pole of the NAcc providing evidence for anatomical specificity of the intra-NAcc induced promotion of memory. In the second experiment, possible mnemonic and reinforcing effects of HA (0.001-1 microg) were gauged after injection of the amine into the caudal NAcc, using post-trial application in the uphill avoidance task to assess effects on learning and place preference as an index of reinforcing properties. The data show that caudal-NAcc injection of HA (0.1 microg) improved retention of the avoidance task and produced place preference indicative of a reinforcing action. The finding that intra-NAcc injection of HA can facilitate learning and has reinforcing effects is at variance with the proposed inhibitory nature of neuronal HA in reward-related processes. Thus, the disinhibition of reinforcement and facilitation of learning found earlier after partial destruction of TM-intrinsic neurons might not necessarily be related to a lesion-induced reduction of the HAergic tone. The observation that CPR has behavioral effects quite similar to HA suggests that the mnemoactive and reinforcing action of this compound might involve pharmacodynamic aspects beyond its antagonistic activity at H1-receptive sites.

Experimental assignment of the structure of the transition state for the association of barnase and barstar

Association of a protein complex follows a two step reaction mechanism, with the first step being the formation of an encounter complex which evolves into the final complex. Here we present new experimental data for the association of the bacterial ribonuclease barnase and its polypeptide inhibitor barstar which shed light on the thermodynamics and structure of the transition state and preceding encounter complex of association at diminishing electrostatic attraction. We show that the activation entropy at the transition state is close to zero, with the activation enthalpy being equal to the free energy of binding. This observation was independent of the magnitude of the mutual electrostatic attraction, which were altered by mutagenesis or by addition of salt. The low activation entropy implies that the transition state is mostly solvated at all ionic strengths. The structure of the transition state was probed by measuring pairwise interaction energies using double-mutant-cycles. While at low ionic strength all proximal charge-pairs form contacts, at high salt only a subset of these interactions are maintained. More specifically, charge-charge interactions between partially buried residues are lost, while exposed charged residues maintain their ability to form specific interactions even at the highest salt concentration. Uncharged residues do not interact at any ionic strength. The results presented here suggest that the barnase-barstar binding sites are correctly aligned during the transition state even at diminishing electrostatic attraction, although specific short range interactions of uncharged residues are not yet formed. Furthermore, most of the interface desolvation (which contributes to the entropy of the system) has not yet occurred. This picture seems to be valid at low and high salt. However, at high salt, interactions of the activated complex are limited to a more restricted set of residues which are easier approached during diffusion, prior to final docking. This suggest that the steering region at high salt is more limited, albeit maintaining its specificity.

Superior water maze performance and increase in fear-related behavior in the endothelial nitric oxide synthase-deficient mouse together with monoamine changes in cerebellum and ventral striatum

Nitric oxide (NO) has been implicated in the control of emotion, learning, and memory. We have examined endothelial NO synthase-deficient mice (eNOS-/-) in terms of habituation to an open field, elevated plus-maze behavior, Morris water maze performance, and changes in cerebral monoamines. In the open field, eNOS-/- animals were less active than wild-type controls but showed unimpaired habituation. In the plus-maze, an anxiogenic effect was observed. Proceeding from previous findings of deficits in hippocampal and neocortical long-term potentiation (LTP) in our eNOS-/- mice, we investigated whether these animals also express deficits in learning tasks that have been linked to hippocampal function and LTP. Unexpectedly, eNOS gene disruption led to accelerated place learning in the water maze. Furthermore, during long-term retention and reversal learning, eNOS-/- mice showed improved performance. In a cued version of the water maze task, eNOS-/- and control mice did not differ, implying that the superior performance of eNOS-/- animals on the former tasks cannot be attributed solely to differences in sensorimotor capacities. The neurochemical evaluation of the eNOS-/- mice revealed increases in the concentrations of the serotonin metabolite 5-HIAA in the cerebellum, together with an accelerated serotonin turnover in the frontal cortex. Furthermore, eNOS-/- mice had a higher dopamine turnover in the ventral striatum. These findings are discussed in terms of possible concomitant effects on physiological parameters, such as a decreased reactivity of GABAergic neurotransmission or changes in vascular functions, and effects on behavioral processes related to reinforcement, learning, and emotion.

Memory improvement by post-trial injection of lidocaine into the tuberomammillary nucleus, the source of neuronal histamine

Brain histamine is exclusively contained within and released from neurons whose cell bodies are clustered in the tuberomammillary nucleus (TM) of the posterior hypothalamus. This experiment examined the effects of a transient inactivation of the TM on inhibitory avoidance learning. Rats with chronically implanted cannulae were tested on a 1-trial step-through avoidance task. Immediately following training, the rats received unilateral intra-TM infusions (0.5 microl) of lidocaine (5 or 20 microg). Control groups included vehicle-injected rats and a group given an injection of 20 microg lidocaine 5 h after training. When tested 24 h later, rats treated with 20 microg lidocaine exhibited longer step-through latencies than vehicle-treated controls, indicative of superior learning of the task. The failure of the delayed post-trial injection of lidocaine to significantly influence step-through latencies indicates that the compound influenced learning by modulating memory storage processes rather than by acting on performance variables during retrieval of the task. Thus, inactivation of the TM by lidocaine can exert facilitatory effects on mnemonic processing, which might be related to a temporary reduction of histaminergic activity during the early phase of memory consolidation.

A phage-based system to select multiple protein-protein interactions simultaneously from combinatorial libraries

Selectively infective phage (SIP) can be used to identify protein-protein interactions. SIP was modified to facilitate the simultaneous selection of interacting protein pairs from large combinatorial libraries. An interference-resistant phage was constructed which non-covalently, but stably links the genetic information of an interacting pair, encoded separately on phage and phagemid vectors, by co-packaging into heteropolyphages. In a model system, the interaction between a SIP-selected peptide and the intracellular domain of the p75 neurotrophin receptor was detected in the presence of a 10(4)-fold excess of a non-interacting control pair (jun leucine zipper and p75 intracellular domain) via SIP hetero-polyphage transductants. To minimize the redundancy of transductants and to minimize possible ligand exchange generated in a solution-based SIP screening, a filter-based in situ infectivity screening was developed. The combination of the above techniques may provide a powerful system for rapid screening of very large sequence spaces.

Anxiolytic-like behavior after lesion of the tuberomammillary nucleus E2-region

The tuberomammillary nucleus (TM), located in the posterior hypothalamic region, consists of five subgroups and is the only known source of brain histamine. In the present experiment, rats received bilateral ibotenic acid or sham lesions in the rostroventral part of the TM (E2-region). Three weeks later they were tested on the elevated plus-maze test of fear and anxiety. Lesions in the tuberomammillary E2-region elevated the time spent on the open arms, as well as excursions into the end of the open arms, increased scanning over the edge of an open arm, and decreased risk-assessment from an enclosed arm. Thus, partial destruction of TM intrinsic neurons can induce anxiolytic-like effects which are possibly related to a lesion-induced reduction of histaminergic activity.

Facilitation of learning after lesions of the tuberomammillary nucleus region in adult and aged rats

The tuberomammillary nucleus (TM) located in the posterior part of the hypothalamus is the main source of neuronal histamine in the central nervous system. Recent work from our laboratories has indicated an involvement of the TM region in neuronal plasticity and reinforcement processes. In the present study, we investigated the effects of TM lesions on the performance of adult and aged Wistar rats in a set of learning tasks, which differed in terms of complexity and reward contingencies (habituation learning, inhibitory avoidance, discrimination learning, Morris water maze). An improvement was found in every test applied, indicating that TM lesions seem to generally enhance learning and memory capacities independent of the special demands of a given task. Age-related learning deficits were strongly diminished. Immunohistochemistry revealed that the excitotoxic lesions used to destroy the TM region led to a marked decrease in the number of histamine-positive neurons in the vicinity of the injection site, indicating an involvement of the brain histaminergic system in the observed behavioral changes.

Dissociation between anxiolytic and hypomnestic effects for combined extracts of zingiber officinale and ginkgo biloba, as opposed to diazepam

Previous work has shown that Zingicomb (ZC), a combination preparation of zingiber officinale and ginkgo biloba, exerts anxiolytic-like effects in the elevated plus-maze (EPM), possibly related to 5-HT antagonistic properties of its components. The first experiment of this study was performed to gauge the specificity of the anxiolytic action of ZC with respect to the mixture ratio of the single components in the combination preparation. Two different combinations of zingiber officinale and ginkgo biloba extracts (ratio of components: 1:1 or 1:2.5) were compared with the standard ratio adjusted for ZC (2.5:1). Each combination was administered intragastrically (I.G.) in five doses (0.01 to 10 mg/kg) before the rats were tested on the EPM. Zingicomb at 1 mg/kg elevated the time spent on the open arms, scanning of the open arms and excursions into the ends of the open arms, whereas the two other combinations (1:1 and 1:2.5) did not influence rats' behavior on the EPM in the entire dose range tested. With regard to the memory-disrupting effects of anxiolytics, particularly of diazepam (DZP), a second experiment was performed to compare the effects of ZC (0.5, 1, 10 mg/kg, I.G.) and DZP (1 or 5 mg/kg, I.P.) on the performance of rats in two different learning tasks. Rats were treated with DZP or ZC prior to the learning trial of a one-trial step-through inhibitory avoidance task. Retention testing 24 h later showed impaired retention for rats injected with DZP at 5 mg/kg but not for animals that had received ZC prior to training. In a further experiment, rats were treated once daily with DZP or ZC prior to the training trials in a water maze. Injections of DZP at 5 mg/kg impaired place and cue learning, whereas the treatment with ZC did not influence the navigation performance in the maze. The present results indicate that the anxiolytic-like effects of ZC are specific in that only the mixture ratio of zingiber officinale and ginkgo biloba adjusted for the phytopharmacon was active in the EPM. Furthermore, ZC did not interfere negatively with the performance on an inhibitory avoidance and a water maze task, as opposed to DZP. This finding is interesting with regard to other studies that have revealed a similar dissociation between anxiolytic and memory-disrupting effects for chemically defined 5-HT antagonists, especially for those acting at 5-HT3 receptors.

Evidence for anatomical specificity for the reinforcing effects of SP in the nucleus basalis magnocellularis

Previous studies have shown that substance P (SP) exerts reinforcing effects following injection into the region of the nucleus basalis magnocellularis (NBM) in rats. The aim of the present study was to further characterize this effect by examining its anatomical specificity. Reinforcing effects of SP were assessed following unilateral microinjection into the NBM or into the nearby rostral part of the ventral pallidum (VP), using conditioned place preference as an index for reinforcement. Intracranial injection of SP was performed through small diameter glass micropipettes which allowed precise delivery of SP in minute quantities. A single microinjection of SP (0.2 and 1 ng) into the NBM produced a conditioned place preference, whereas injection of SP into the rostral VP failed to alter the preference behavior. The results confirm that SP has reinforcing effects when administered into the NBM and provide evidence that these effects are brain-site specific.

The role of Glu73 of barnase in catalysis and the binding of barstar

Barnase, a small extracellular ribonuclease from Bacillus amyloliquefaciens and its intracellular inhibitor barstar have co-evolved to bind tightly and rapidly. Barnase has also evolved to be catalytically active. The active site of barnase and its binding site for barstar use the same subset of amino acids. The exception is Glu73 (the general base in catalysis), which although located at the centre of the binding site, is separated by three ordered water molecules from barstar. We examined in this work the contribution of Glu73 to both catalysis and barstar binding. Truncation mutants of the general base (Glu73 --> Ala or Ser) retain a residual RNase activity of about 0.3% while mutants with larger hydrophobic replacements (Glu 73 --> Trp or Phe) have virtually no catalytic activity. This, and binding data of 3'-GMP with the different barnase mutants suggest that the loss in activity results from the elimination of the general base, which can be substituted to some extent by water or other polar side-chains in truncation mutants. All of the Glu73 mutations lead to a weakening of the free energy of complex formation with barstar by 1.4 to 3.0 kcal/mol (including Gln). This is surprising, since Glu73 does not interact directly with barstar and there is an electrostatic repulsion between Glu73 on barnase and the negatively charged binding surface of barstar. A newly developed method of constructing double mutant cycles between multiple mutations at the same site appears to pinpoint a favourable interaction between Glu73 and one of its nearest neighbours in barstar, Asp39. The coupling energy between those residues is presumably indirect: the carboxylate of Glu73 organizes neighbouring positively charged groups in barnase, Lys27, Arg83, and Arg87 to interact with Asp39 in barstar. This emphasizes that an apparent interaction between a pair of residues as measured with double mutant cycles is the sum of their direct and indirect interactions.

The histamine H1-antagonist chlorpheniramine facilitates learning in aged rats

The effect of the histamine H1-receptor antagonist chlorpheniramine on inhibitory avoidance conditioning was investigated in 31-month-old rats, using a one-trial step-through avoidance task. Immediately after the learning trial, old rats were injected intraperitoneally with 5 or 10 mg/kg d-chlorpheniramine. Control groups included vehicle-injected old and adult (4-month-old) rats and a group of aged animals given an injection of 10 mg/kg chlorpheniramine 5 h after the training trial. When tested 24 h after training, aged rats receiving 10 mg/kg chlorpheniramine exhibited longer step-through latencies than vehicle-treated old controls, indicative of superior learning of the task. The hypermnestic effects of 10 mg/kg chlorpheniramine were no longer evident when injection was performed 5 h, rather than immediately after the learning trial, ruling out enduring proactive effects of the treatment on test performance. Furthermore, vehicle-treated old rats showed poorer inhibitory avoidance performance than vehicle-treated adult controls. Thus, the improvement in performance after the 10 mg/kg dose of chlorpheniramine can be interpreted in terms of a compensation of performance deficits in the old rats.

Thermodynamics of the interaction of barnase and barstar: changes in free energy versus changes in enthalpy on mutation

We have studied the thermodynamics of the interaction between the ribonuclease barnase and its natural polypeptide inhibitor barstar. The contribution of specific residues and interactions within the barnase-barstar interface to the enthalpy of binding has been examined using isothermal titration calorimetry and protein engineering. The enthalpy of association of the wild-type proteins is -18.9 (+/-0.1) kcal/mol at pH 8 and at 25 degrees C. The enthalpy of binding remains favourable for 31 different combinations of mutations in the interface. The effects on the binding enthalpy upon replacing a side-chain involved in the interaction of barnase and barstar are, however, always unfavourable and in most cases larger than the effects on the free energy of binding. Interaction enthalpies calculated by double mutant cycle analysis are in some cases much larger than the interaction free energies. The interaction enthalpies for complexes between different barnase mutants with amino acid substitutions of the general base residue glutamic acid 73 and a barstar variant (D39A) vary by as much as 8.3 kcal/mol while the coupling free energies differ only by 1 kcal/mol. The use of enthalpies for the analysis of structure-activity relationships appears to be complicated by enthalpy-entropy compensation of weak intermolecular interactions. These tend to cancel out in measurements of free energy, which is thus the preferred quantity for simple analysis of interactions.

Contribution of the intramolecular disulfide bridge to the folding stability of REIv, the variable domain of a human immunoglobulin kappa light chain

BACKGROUND

Immunoglobulin domains contain about 100 amino acid residues folded into two beta-sheets and stabilized in a sandwich by a conserved central disulfide bridge. Whether antibodies actually require disulfide bonds for stability has long been a matter of debate. The contribution made by the central disulfide bridge to the overall folding stability of the immunoglobulin REIv, the variable domain of a human kappa light chain, was investigated by introducing stabilizing amino acid replacements followed by removal of the disulfide bridge via chemical reduction or genetic substitution of the cysteine residues.

RESULTS

Nine REIv variants were constructed by methods of protein engineering that have folding stabilities elevated relative wild-type REIv by (up to) 16.0 kJ mol-1. Eight of these variants can be cooperatively refolded after unfolding and chemical reduction of the disulfide bridge-in contrast to wildtype REIv. The stabilizing effect of one of these residue replacements (T39K) was rationalized by determining the structure of the respective REIv variant at 1.7 A. The loss of folding stability caused by reduction of the intramolecular disulfide bond is on average 19 kJ mol-1. Removal of the disulfide bridge by genetic substitution of C23 for valine resulted in a stable immunoglobulin domain in the context of the stabilizing Y32H amino acid exchange; again, REIv-C23V/Y32H has 18 kJ mol-1 less folding stability than REIv-Y32H. The data are consistent with the notion that all variants studied have the same overall three-dimensional structure with the disulfide bridge opened or closed.

CONCLUSIONS

A comparison of the magnitude of the stabilizing effect exerted by the disulfide bond and the length of the mainchain loop framed by it suggests lowering of the entropy of the unfolded state as the sole source of the effect. Disulfide bonds are not necessary for proper folding of immunoglobulin variable domains and can be removed, provided the loss of folding stability is at least partly compensated by stabilizing amino acid exchanges.

Blockade of lithium chloride-induced conditioned place aversion as a test for antiemetic agents: comparison of metoclopramide with combined extracts of Zingiber officinale and Ginkgo biloba

The present study tests the hypothesis that the blockade of lithium chloride-induced conditioned place aversion might be a suitable model to assess antiemetic properties of drugs, especially in species that do not vomit, like rats. The effects of the known antiemetic compound metoclopramide were compared with those of zingicomb, a combination preparation of extracts of Ginkgo biloba and Zingiber officinale, also presumed to have antiemetic properties. Place conditioning was performed using a conventional three-compartment test procedure. On three successive conditioning trials, rats received an intraperitoneal (i.p.) injection of lithium chloride (125 mg/kg) and were placed into the compartment that they had preferred over three baseline trials. During the test, rats treated with lithium chloride (LiCl) spent less time in the treatment compartment, indicative of a conditioned place aversion (CPA). In the first experiment, metoclopramide (MCP) was administered intragastrically (IG) in doses of 2 or 10 mg/kg 60 min prior to LiCl injection. The pretreatment with 50 and 100 mg/kg zingicomb attenuated the LiCl-produced CPA, whereas a dosage of 10 mg/kg had no effect. These findings suggest that LiCl-induced CPA is a viable procedure with which to assess the antiemetic properties of metoclopramide. Furthermore, the data confirm the hypothesis that the phytopharmacon zingicomb might have antiemetic properties that are comparable to those of metoclopramide.

Facilitation of learning following injection of the chondroitin sulfate proteoglycan biglycan into the vicinity of the nucleus basalis magnocellularis

The aim of this study was to examine the effects of biglycan, a small chondroitin sulfate proteoglycan with neurotrophic activity, on memory and reinforcement upon unilateral injection into the region of the nucleus basalis magnocellularis (NBM). In experiment 1, rats with chronically implanted cannulas were injected with biglycan and tested on the uphill avoidance task, which involves punishment of a high-probability turning response on a tilted platform (negative geotaxis). Immediately after the training trial, that is, after a tail-shock was administered upon performing the response, rats received one microinjection (0.5 microliter) of substance P (SP) in a reference dosage of 0.74 pmol or biglycan (doses ranging from 1.3 to 1300.0 nmol) into the NBM region. When tested 24 h later, rats treated with SP (0.74 pmol) or biglycan (2.1 and 2.6 nmol) had significantly longer uphill latencies than vehicle (PBS) controls, indicative of superior learning of the avoidance response. In experiment 2, a test for possible proactive effects of post-trial biglycan on performance during the retention trial was performed. Furthermore, the uphill avoidance task was combined with a conditioned place preference task to assess possible reinforcing effects of biglycan. Rats were injected with either 2.6 or 130.0 nmol biglycan immediately after the training trial of the uphill task. One control group received 2.6 nmol biglycan 5 h after the trial, a second group was sham-operated. Additional groups were included which received biglycan (2.6 or 130.0 nmol), SP (0.74 pmol) or PBS after the training trial but no tail-shock.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunoglobulin mutant library genetically screened for folding stability exploiting bacterial signal transduction

A model repertoire of variants of immunoglobulin kappa variable domain REIv with different folding stabilities was generated by oligonucleotide-directed randomization of position 29, a key conserved residue of hypervariable loop 1. Fused to ToxR', the membrane-anchored cytoplasmic domain of the Vibrio cholerae ToxR transcription activator, different members of the library induce different levels of transcription from the ctx promoter in Escherichia coli. Differences in transcription activation correlate positively with folding stabilities of the corresponding REIv domains. Since conformationally stabilized REIv derivatives elicit a dark red colony phenotype on EMB-lactose indicator plates, this procedure constitutes a genetic screen for immunoglobulin folding stability.

Characterization of in vitro oxidized barstar

The polypeptide inhibitor of the ribonuclease barnase, barstar, has two cysteine residues in positions 40 and 82. These have been proposed to form a disulfide bridge leading to an increase in stability without changing the inhibitory activity of the protein. Barstar and a mutant (E80A) were oxidized in vitro and the biochemical and physico-chemical properties of the oxidized monomers were analysed. The oxidized proteins show no inhibition of barnase using a plate assay and are significantly destabilized. CD spectra indicate a loss of secondary structure. The amino acid substitution E80 --> A stabilizes the oxidized barstar to about the same extent as it does the reduced protein, indicating, however, that the helical region which it is in is intact.

Self-administration of neurokinin substance P into the ventromedial caudate-putamen in rats

There is evidence that the neurokinin substance P plays a role in learning and reinforcement processes. Reinforcing effects of substance P were found upon injection into several parts of the brain. The aim of the present study was to gauge possible reinforcing effects of microinjections of substance P into the ventromedial caudate-putamen in rats. Two different behavioral paradigms were employed. In the first experiment a two-compartment choice procedure was used and the rats could trigger substance P injections (500 pg per 5 nl injection volume) into the ventromedial caudate-putamen by entering one distinctive compartment. During the injection period, substance P-injected animals spent significantly more time in the drug-paired compartment than vehicle-injected controls. In the second experiment, nose-poking through a hole in one wall of the cage was used as the operant. Rats that could self-administer substance P (100 pg per 5 nl injection volume) into the ventromedial caudate-putamen emitted a significantly higher rate of operant responding on the first day of testing and a significantly lower rate on the third day compared to vehicle-injected animals. The experiments provide evidence that the administration of substance P into the ventromedial part of the caudate-putamen can have positive reinforcing effects, but that repeated injections can have aversive properties. These effects are discussed, firstly, with regard to the possible mechanisms of intrastriatal substance P on striatonigral and striatopallidal output systems and, secondly, with respect to their possible relevance in the study of the basal forebrain reinforcement system.

Chronic administration of neurokinin SP improves maze performance in aged Rattus norvegicus

Deficits in associative functions seen with senescence may be based, at least in part, on a decreased availability of trophic factors in the CNS. A reduced concentration of neurokinins, including undecapeptide substance P (SP), also accompanies aging. Thus, given the change in SP metabolism and the known mnemogenic as well as neurotrophic/neuroprotective effects of the peptide, it seems possible that age-related deficits in associative processes could be influenced by treatment with exogenous SP. In the present study, 30-month-old Wistar rats were injected daily with SP (50 or 250 micrograms/kg, intraperitoneally) starting 1 week before they were tested on the Morris water maze task and on motor coordination tests. Control groups included vehicle-injected old and adult (3-month-old) rats. Over the days of maze testing, application of the substances was performed 5 h after testing daily for 15 days and after the last drug delivery, maze testing was continued for 4 more days. The main finding of this study is that chronic administration of both dosages of SP (50 and 250 micrograms/kg) improved the maze performance of the old rats. This facilitatory effect of SP on performance was also evident after the drug treatment had been terminated in the course of maze testing. Furthermore, chronic application of SP in a dose range of 50-250 micrograms/kg was found to reduce age-related deficits in motor capacities.

A soluble immunoglobulin variable domain without a disulfide bridge: construction, accumulation in the cytoplasm of E. coli, purification and physicochemical characterization

Two amino acid exchanges (Y32H and C23V) were introduced sequentially into the immunoglobulin REIV, a human kappa variable domain. The first exchange stabilizes the folded state of the domain by 4.6 kJ/mol (1.1 kcal/mol), the second abolishes the central disulfide bridge and destabilizes the folded domain by 17.5 kJ/mol (4.2 kcal/mol). Introduction of the stabilizing exchange first is a necessary pre-requisite to the removal of the central disulfide bridge without collapse of the fold. The double mutant REIV-C23V/Y32H can be accumulated in the cytoplasmatic compartment of the E. coli cell, a finding that opens new possibilities in antibody engineering.

Dimerization of Bence Jones proteins: linking the rate of transcription from an Escherichia coli promoter to the association constant of REIV

Homodimers of immunoglobulin VL domains are minimal models of antibodies in that they display an ensemble of six hypervariable loops. Bence Jones protein REI is a mixture of a complete kappa light chain and the corresponding variable domain (REIV). The known three-dimensional structure of the REIV dimer (Epp et al., 1975, Biochemistry 14, 4943-4952) provides a basis for studying dimer stabilization by protein engineering. Mutant REIV-L94H was constructed and shown to have an equilibrium constant of dimerization about one order of magnitude higher than wildtype REIV. By fusing REIV and variants to the aminoterminal part of the Vibrio cholerae ToxR regulator protein (Miller et al., 1987, Cell 48, 271-279), a transcriptional signal in E. coli can be derived from REIV homodimer formation constant. The system senses dimerization of the immunoglobulin part of the fusion protein, located in the periplasmatic space, and transduces the signal as transcriptional activation to a ctx::lacZ gene construct integrated into the E. coli chromosome. There is positive correlation between the propensities of homodimer formation and the rate of transcriptional initiation at the ctx promoter. Since beta-galactosidase levels can easily be measured colorimetrically in crude cell lysates of a large number of clones using an ELISA reader, this procedure constitutes all elements required for a genetic screen in E. coli for immunoglobulin variants with altered association constants.

[Sonography of the salivary glands]

358 sonographic studies of the salivary glands of 255 patients with proven diagnoses were evaluated retrospectively. Sonography proves to be highly valuable to differentiate between peri- and intraglandular lesions (98%). Superficial neoplasms can be delineated easily. A sharp margin of the tumour is not reliable to predict benignity, therefore biopsy should be performed in all neoplasms of the glands. Deep infiltrating processes require further evaluation by CT or MR. In cases with sialolithiasis the stones can be demonstrated in approx. 2/3 by ultrasound. Inflammatory diseases of the salivary glands have variant sonographic features. Acute infections usually have hypoechogenic parenchyma, chronic inflammations are more likely hyperechogenic.

Studies of the protein synthesis system in the brain cortex during global ischemia and reperfusion

Previous studies have demonstrated that brain protein synthesis declines after global ischemia and reperfusion. To investigate the role of the translation system in this phenomenon, we examined the ability of partially purified ribosomes, ribosome-bound mRNA and translation cofactors derived from the transiently ischemic cerebral cortex to synthesize protein in vitro. Samples were prepared from canines subjected to 20-min cardiac arrest and after 2 or 8 h of post-resuscitation intensive care. There was no significant decrease in the rate of in vitro protein synthesis as a consequence of either ischemia or reperfusion. Northern hybridization of ribosome-bound RNA revealed a discrete band of mRNA for brain-specific creatine kinase (ck-bb) that was consistent in presence and intensity in all groups. However, mRNA for heat shock 70 protein (hsp-70) was observed only during reperfusion and markedly increased between 2 and 8 h reperfusion. Thus, we conclude that (1) the transcription system is intact during reperfusion and hsp-70 mRNA is made and translocated to the ribosomes during reperfusion, (2) mRNA for ck-bb is not displaced from ribosomes by the appearance of hsp-70 during reperfusion and (3) isolated ribosomes maintain their ability to translate in vitro during the first 8 h of reperfusion after global brain ischemia. Therefore, the early reduction in protein synthesis observed in vivo during post-ischemic brain reperfusion is not due to an intrinsic dysfunction of the ribosomes.

Occupational exposure to amorphous silica dust and pulmonary function

Respiratory manifestations among 41 workers exposed to amorphous silica dust were compared with a control group comprising 90 workers of equivalent socioeconomic state in the same plant. Flow volumes were determined, blood gas concentrations were measured at rest and during exercise, chest radiographs were obtained, and data about respiratory symptoms were collected by questionnaire. A dust exposure index was calculated for each exposed worker. It was not possible to differentiate between the two groups from the questionnaire, blood gas analysis, or chest radiographs. On the other hand, the tests of respiratory function showed a significant decrease in forced expiratory flow (FEF25-75, FEF50, and FEF75) in the exposed group compared with the controls, although no correlation was found between the exposure index and pulmonary function. It appears that smoking and exposure to amorphous silica synergise to induce small airway disease.

[Inhibition of degranulation of human basophils by calcium antagonists]

The human basophil degranulation test (HBDT) quantifies the apparent disappearance of basophils after contact with the sensitizing allergen. The inhibition of degranulation by pharmacological products can be appreciated by incubating beforehand the basophils with the substance concerned during various times. The inhibitory effect is evaluated by the difference of degranulation with or without it. EDTA, sodium cromoglycate, verapamil and bepridil have been tested at different concentrations and at 3 times of basophils preincubation (0,15 and 30 minutes). Results obtained confirm previous reports concerning cromoglycate which didn't inhibit degranulation of basophils. EDTA at 3.4*10(-2)M and 3.4*10(-3)M concentration has an inhibitory effect, not increasing with the time of preincubation. The inhibition with verapamil is of the same order at 1*10(-4)M for the 3 times of incubation and weaker, but significant, at 1*10-M5 after 30 minutes of preincubation. Bepridil inhibits at 1*10(-4)M, but this effect disappears if basophils are preincubated 30 minutes with the drug. The inhibition of the specific basophil degranulation by these drugs is probably du to their calcium antagonist property. However their effect is not quite similar when cells are preincubated at different times with the drug. On the other hand, one can study with HBDT the inhibitory effect of a new product, even if the therapeutic indications would have to be studied afterwards.

Improved results in acute appendicitis care following areawide review

The Wisconsin Professional Review Organization compared acute appendectomies being performed in 1981 to those done in 1978 in 32 Wisconsin hospitals. In both years approximately 75 percent of primary appendectomies were in patients 5 to 30 years of age, one-fourth were in patients 15 to 19 years of age, and the majority were in males. Incidence of normal appendices dropped from 16.1 percent in 1978 to 11.4 percent in 1981 (p less than 0.005). The number of patients with normal appendices who did not meet symptom criteria dropped from 37.3 percent to 9.5 percent (p less than 0.05). Incidence of normal appendices was highest in small hospitals. Severity and ruptures or perforations increased, but not significantly. Postoperative complications and mortality decreased. Average length of stay decreased overall, but increased for patients with complications and ruptures or perforations. These data suggest that areawide reviews assure quality and help contain costs. Physician self-regulation using areawide studies may produce desirable change.